For the longest time: Quantum computing engineers set new standard in silicon chip performance

It takes two thousandths of a second for quantum computing to work. The blink of an eye at one tenth of a second is long.

A group of researchers at the University of New South Wales have shown that spin qubits can hold up to two milliseconds. The duration of time that qubits can be manipulated in increasingly complicated calculations is known as 'coherence time'.

Ms Seedhouse's work in theoretical quantum computing contributed to the achievement.

The coherence time tells you how long you can do all of the operations before you lose all the information.

The more spins you can keep, the better the chance that the information can be kept up to date. Values are lost when spin qubits stop spinning. Extending coherence was confirmed by quantum engineers at the University of New South Wales.

If quantum computers are to solve some of humanity's biggest challenges, like the search for effective vaccines, modelling weather systems and predicting the impacts of climate change, they'll need to keep track of millions of qubits.

Engineers have been trying to figure out how to manipulate millions of qubits without generating more heat and interference for decades. Rather than adding thousands of tiny antennas to control millions of electrons with magnetic waves, the research team came up with a way to use just one antenna to control all the qubits. The results were published in a scientific journal.

This solved the problem of space, heat and noise that would inevitably increase as more and more qubits are brought online to carry out the mind-bending calculations that are possible when qubits not only represent 1 or 0, but both at once, using a phenomenon known as quantum

Individual control versus global control.

There are a few challenges to be solved by this proof-of- concept achievement. The last paper published this week was one of a series of papers that Ms Ingvild Hansen and Ms Seedhouse wrote together.

It was a big step forward to be able to control millions of qubits. Control of millions of qubits at once is a great achievement, but working quantum computers will need to be manipulated individually. The spin qubits will have the same values if they are at the same Frequency. How can we control them in a way that they don't represent the same values?

The first thing we showed was that we can improve the coherence time by continuously rotating the qubits.

The performance can continue if you imagine a circus performer spinning plates. If we keep driving qubits, they can hold information for longer. The coherence times of such qubits were more than 200 microseconds.

The next challenge was to make the protocol more robust and to show that the globally controlled electrons can be controlled individually so that they could hold different values needed for complex calculations.

The 'SMART' qubit protocol was created by the team and it was able to achieve this.

They used qubits to rock back and forth like a metronome. If an electric field is applied individually to any qubit, it can be put into a different rhythm than its neighbours.

Ms Seedhouse says it's like two kids on a swing who are going in opposite directions. One can be a 0 when the other is a 1 if we push them to reach the end of their arcs.

The result is that a qubit can be controlled individually and under the influence of global control.

One of the senior researchers in the team says that they have shown a simple and elegant way to control all qubits at the same time.

There is a potential path for full-scale quantum computers.

Professor Andrew Dzurak is the CEO and founder of Diraq, a company that is developing quantum computer processors which can be made using standard Silicon chip manufacturing.

Next step.

"Our next goal is to show this working with two-qubit calculations after showing our proof-of-concept in our paper with one qubit," she said.

To show that the theory is proven in practice, we want to demonstrate that we can do this for a few qubits.

More information: Amanda E. Seedhouse et al, Quantum computation protocol for dressed spins in a global field, Physical Review B (2021). DOI: 10.1103/PhysRevB.104.235411

Ingvild Hansen and his colleagues wrote about pulse engineering of a global field for quantum computation. There is a DOI titled "10.103/PhysRevA. 104.062415".

The implementation of an advanced dressing protocol for global qubit control was done by I. Hansen and his team. The DOI is 10.1063.